Pelosi: Natural gas "clean, cheap alternative to fossil fuels"

Speaker of the House, Nancy Pelosi, seems unclear on the concept of "fossil fuels", as evidenced by this doozy from a Meet the Press interview with Tom Brokaw:

... I'm, I'm, I'm investing in something I believe in. I believe in natural gas as a clean, cheap alternative to fossil fuels. ...

Transcript here. Sigh.